KmsMasterKeyProvider regionalClientSupplier_ does not appear to be getting set correctly by default

[mattsb42-aws]

When a KmsMasterKeyProvider is constructed using the default builder[1] and is then used to attempt to decrypt a ciphertext message from another region, the decrypt call fails with this error[2].

It appears that something is not connecting with the default supplier in build()[3].

[1] KmsMasterKeyProvider.builder().build()
[2]

aws-encryption-sdk-java/src/main/java/com/amazonaws/encryptionsdk/kms/KmsMasterKeyProvider.java

Line 526 in 6cb1c42

throw new AwsCryptoException("Can't use keys from region " + regionName_);

[3]

aws-encryption-sdk-java/src/main/java/com/amazonaws/encryptionsdk/kms/KmsMasterKeyProvider.java

Lines 245 to 259 in 6cb1c42

	public KmsMasterKeyProvider build() {
	// If we don't have a default region, we need to check that all key IDs will be usable
	if (defaultRegion_ == null) {
	for (String keyId : keyIds_) {
	if (parseRegionfromKeyArn(keyId) == null) {
	throw new AwsCryptoException("Can't use non-ARN key identifiers or aliases when " +
	"no default region is set");
	}
	}
	}
	RegionalClientSupplier supplier = clientFactory();
	return new KmsMasterKeyProvider(supplier, defaultRegion_, keyIds_, emptyList(), false);
	}